| /* VMString.java -- VM Specific String methods |
| Copyright (C) 2003 Free Software Foundation |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package java.lang; |
| |
| import java.lang.ref.WeakReference; |
| import java.util.WeakHashMap; |
| |
| /* |
| * This class is a reference version, mainly for compiling a class library |
| * jar. It is likely that VM implementers replace this with their own |
| * version that can communicate effectively with the VM. |
| */ |
| |
| /** |
| * Code relocated from java.lang.String by |
| * @author Dave Grove <groved@us.ibm.com> |
| */ |
| final class VMString |
| { |
| |
| /** |
| * Holds the references for each intern()'d String. If all references to |
| * the string disappear, and the VM properly supports weak references, |
| * the String will be GC'd. |
| */ |
| private static final WeakHashMap internTable = new WeakHashMap(); |
| |
| /** |
| * Fetches this String from the intern hashtable. If two Strings are |
| * considered equal, by the equals() method, then intern() will return the |
| * same String instance. ie. if (s1.equals(s2)) then |
| * (s1.intern() == s2.intern()). All string literals and string-valued |
| * constant expressions are already interned. |
| * |
| * @param str the String to intern |
| * @return the interned String |
| */ |
| static String intern(String str) |
| { |
| synchronized (internTable) |
| { |
| WeakReference ref = (WeakReference) internTable.get(str); |
| if (ref != null) |
| { |
| String s = (String) ref.get(); |
| // If s is null, then no strong references exist to the String; |
| // the weak hash map will soon delete the key. |
| if (s != null) |
| return s; |
| } |
| internTable.put(str, new WeakReference(str)); |
| } |
| return str; |
| } |
| |
| } // class VMString |